Slot antenna with programmed radiation pattern



E. SPITZ April 9, 1968 SLOT ANTENNA WITH PROGRAMMED RADIATION PATTERN 6 Sheets-Sheet 1 Filed Jan. 29, 1963 April 9, 1968 E. SPITZ 3,377,596

SLOT ANTENNA WITH PROGRAMME!) RADIATION PATTERN Filed Jan. 29, 1963 6 Sheets-Sheet 2 April 9, 1968 E. SPITZ 3,377,596

SLOT ANTENNA WITH PROGRAMMED RADIATION PATTERN Filed Jan. 29.. 1963 6 Sheets-Sheet 5 nu l l l [a I l l l l n l -;i vv2 r I l I I -[o-( I L -no( L.-

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E. SPITZ April 9, 1968 SLOT ANTENNA WITH PROGRAMMED RADIATION PATTERN 6 Sheets-Sheet 4.

Filed Jan. 29, 1963 EZZZZZ April 9, 1968 E. SPITZ 3,377,596

SLOT ANTENNA WITH PROGRAMMED RADIATION PATTERN Filed Jan. 29, 1963 6 Sheets-Sheet 5 a I i o 0 g I 0 4 l 2' I I & 0 l l i i Q v H FI'GJO E. SPITZ A ril 9, 1968 SLOT ANTENNA WITH PROGRAMMED RADIATION PATTERN Filed Jan. 29, 1963 6 Sheets-Sheet 6 FIG. f1

3,377,596 SLOT ANTENNA WITH PROGRAMMED RADIATION PATTERN Erich Spitz, Paris, France, assignor to CSF-Compagnie Generale de Telegraphic Sans Fl], a corporation of France Filed Jan. 2?, 1963, Ser. No. 254,655 Claims priority, application France, Jan. 31, 1962, 886,464, Patent 1,320,855 Claims. (Cl. 343-768) The present invention relates to microwave antennas.

The problem often arises in microwave technique to provide antennas adapted to scan predetermined space portions with the maximum radiation direction varying in time according to a predetermined program.

Electrical or electronic systems have been devised to this effect which require no moving mechanical components. While such systems generally have the advantage of making high scanning velocities possible, they are, in particular those comprising ferrite switches, ill suited for very short waves, for example millimetric waves.

It is an object of the invention to provide an antenna with a programmed radiation pattern which is particularly suitable for millimeter waves.

An antenna according to the invention comprises a stationary elongated energy guiding system having at least one aperture and mechanical means for masking said aperture according to a predetermined pattern.

According to a preferred embodiment of the invention, the stationary system is built up by a waveguide section having a lengthwise slot, the length of said slot being of the order of the wavelength of the radiated energy. The masking system is built up by a ruled surface and is caused to move in such a way that one of the generatrices is always applied to said slot. It is provided with slots and the registering of the stationary and the moving systems determines the radiation pattern of the energy fed to the stationary system.

The invention will be best understood from the following description and appended drawing, wherein:

FIG. 1 is a perspective view of an antenna according to the invention;

FIG. 2 is an end view of the antenna illustrated of FIG. 1;

FIG. 3 is a plane view of the system of FIG. 2;

FIG. 4 shows an example of the programming cylinder in a developed state;

FIG. 5 shows the scanning pattern obtained by means of the systems of FIGS. 1 to 4;

FIGS. 6 and 7 show developments of different programming cylinders;

FIG. 8 shows the scanning pattern of the cylinder of FIG. 7;

FIG. 9 shows another developed programming cylinder;

FIG. 10 shows the scanning pattern corresponding to the cylinder of FIG. 9;

FIG. 11 shows a further form of the programming cylinder; and

FIG. 12 shows a modification.

The antenna illustrated in FIG. 1 comprises a reflector 1 having the shape of a parabolic cylinder and made of a conductive material. Along the focal line of reflector 1, there is mounted a circular waveguide 2. A slot 3 is formed along a generatrix of guide 2.

A cylinder 4, whose axis is parallel to that of cylinder 2, surrounds the latter and is tangent thereto along slot 3. Cylinder 4 can be rotated about its axis by any suitable known means.

FIG. 2 shows an end-view of the system of FIG. 1, the arrow symbolically indicating the rotating motor and the direction of rotation.

States Patent 0 In FIG. 3, there are shown the two cylinders 2 and 4. Cylinder 4 is provided with slots 5 which are equally spaced along a generatrix of the cylinder. During the rotation of the latter, they move past the slot 3 of guide 2. Thus, cylinder 4 will mask portions of slot 3, while leaving the remaining portions 6 thereof free to radiate energy. Those portions are shown hatched in FIG. 3. The width and shape of slot portions 6 depend on those of slots 3 and slots 5.

Cylinder 2 will be referred to hereinafter as the radiating cylinder and cylinder 4 as the programming cylinder.

In the example illustrated, cylinder 2 has a circular cross section and ultra-high frequency energy is propagated therein according to any suitable mode, for example the H mode.

In FIG. 4, the cylinder 4 is shown developed. Slots 5 are formed along a number of generatrices, for example seven, i.e. generatrices G G G G G G and G but their spacing varies from one generatrix to another.

The spacing along generatrix G is M, k being the wavelength in guide 2 of the energy propagating therein.

The spacing along G is k -t-a. The spacing along G is A +2a. The spacing along G is A t-3a. The spacing along G is A a. The spacing along G is )t -2a. The spacing along G is A 3a. a being a given length.

, The system operates as follows:

When generatrix G is in register with slot 3, all the slot portions 6 are fed in phase. The radiation direction r from cylinder 2 in the plane containing slot 3 is perpendicular to this slot. While generatrix G moves past slot 3, the maximum radiation direction forms an angle on with the perpendicular to slot 3; and while generatrix Gj (j='3 0 +3) is moving past slot 3, this angle is equal to jet.

FIG. 5 shows the variations of angle a between the perpendicular to slot 3 and the radiation direction corresponding to various generatrices, assuming that cylinder 4. is rotating with uniform speed. The angle defining the maximum radiation direction varies by steps, while remaining constant as long as a slot 5 is moving past slot 3.

When a single program is provided, i.e. there is a single set of slots on cylinder 4, the time interval '7', during which the radiation is in a predetermined direction, 1s

where N is the number of rotations per minute and n the number of rows of slots, i.e. seven in the case of FIG. 4. The spacing between the adjacent rows of slots is disregarded.

Several programs P P P may also be provided as shown in FIG. 6. The time interval 1- is then 60/Nnp, p being the number of programs.

If it is desired that there should be no idle period between the programs or set of programs, which are continuously repeated, the slOtS corresponding to one program or set of programs are to cover the whole of the circumference of the cylinder. In this case, the transmission will take place according to a sawtooth pattern, as shown in FIG. 5.

In order to insure a continuous scanning, the invention provides several embodiments of the programming cylinder.

FIG. 7 shows a developed programming cylinder. Slotshave their edges parallel to the straight line connecting the centers of the slots occupying the same position in each row. The resulting scanning is then effected as shown in FIG. 8.

In FIG. 9, the slots having the same position in each row have been merged in one continuous cut-out portion 7. Several sets of such cut-outs, corresponding to several programs may be formed in the cylinder. The scanning angle oc=f(t) is illustrated in FIG. 10.

The generatrix G, moving past the slot corresponds to an angle a which varies in the range rx and +a The maximum distance between two consecutive strips is A +a the minimum distance being h a In the preceding figures, the scanning pattern was of the saw-tooth type.

FIG. 11 illustrates the development of a programming cylinder, when it is desired to obtain a continuous program at a slower scanning speed in a predetermined region of the space, say in the vicinity of 11:0.

The slots 7 are somewhat S-shaped, with a linear portion perpendicular to the generatrices; the distance between the linear portions of two consecutive slots is equal to A FIG. 12 shows in cross section an arrangment where cylinder 2 is a rectangular waveguide.

In this case, cylinders 2 and 4, which are arranged as shown, are no longer tangent to one another. Slot 3 is defined by means of traps 8, having a length equal to M4, for preventing any loss of energy between the two guides.

Among the many advantages of the system according to the invention the following may be set forth:

(1) Only the programming cylinder, which has a reduced weight, is rotated.

(2) The rotary motion may have a constant speed, whatever the scanning program.

(3) The scanning rate may be very high. Taking, by way of example, an angular speed of 6000 r.p.m. and about ten programs on the programming cylinder, the scanning rate is of one kc./s.

(4) By a simple modification of the program, which may be done by means of a foil spread on the programming cylinder, the diagram pattern and the scanning law may be readily modified.

Of course, the invention is not limited to the embodiments described which are given solely by way of example.

What is claimed is:

1. Antenna for radiating ultra-high frequency energy, according to a programmed radiation pattern, comprising: a wave guide extending in a predetermined propagation direction, having an elongated aperture extending in said direction; masking means including a wall having a ruled surface having generatrices; means for moving said means, in such a way that one of said generatrices is always applied to said aperture, said wall having a plurality of rows of slots, extending along spaced generatrices thereof, thus unma-sking spaced radiating slots in said guide.

2. Antenna for radiating ultra-high frequency energy, according to a programmed radiation pattern, comprising:

a wave guide having a wall, said wall having an elongated aperture; a masking cylinder having generatrices; means for rotating said cylinder, in such a way that one of said generatrices is always applied to said aperture; said masking cylinder having a plurality of rows of spaced slots respectively extending along a plurality of said generatrices, thus unmasking portions of said aperture for radiating energy.

3. Antenna for radiating ultra-high frequency energy, according to a programmed radiation pattern, comprising: a wave guide having a wall, said wall having an elongated aperture; a masking cylinder having generatrices; means for rotating said cylinder, in such a way that one of said generatrices is always applied to said aperture; said masking cylinder having a plurality of rows of spaced slots respectively extending along a plurality of said generatrices, the distance between said slots not being the same in all of said rows, thus unmasking portions of said aperture.

4. Antenna for radiating ultra-high frequency energy, according to a programmed radiation pattern, comprising: a wave guide having a wall, said wall having an elongated aperture; a masking cylinder having generatrices; means for rotating said cylinder, insuch a way that one of said generatrices is always applied to said apertureysaid masking cylinder having a plurality of rows of spaced slots respectively extending along a plurality of said generatrices, the distance between said slots not being the same in all of said rows, said slots also forming second rows intersecting said generatrices, the slotsof each one of said rows having opposite edges extending along the same straight lines.

5. Antenna for radiating ultra-high frequency energy, according to a programmed radiation pattern, comprising: a wave guide having a wall, said wall having an elongated aperture; a masking cylinder having generatrices; means for rotating said cylinder, in such a way that one of said generatrices is always applied to said aperture; said mask ing cylinder having a plurality of slots intersecting said generatrices, thus unmasking portions of said aperture for radiating energy.

References Cited UNITED STATES PATENTS 2,480,181 8/1949 Breen et al. 343-768 2,534,451 12/1950 Kahan et a1 343-771 X 2,648,003 8/1953 Chn 343768 2,670,436 2/1954 Dun-bar 343-468 X 2,711,440 6/1955 Rines 343771 XR 3,018,479 1/1962 Kelly 343-768 FOREIGN PATENTS 886,164 8/1953 Germany.

ELI LIEBERMAN, Primary Examiner.

HERMAN KARL SAALBACH, C. L. JUSTUS,

Examiners.

T. H. TUBBESING, Assistant Examiner.- 

1. ANTENNA FOR RADIATING ULTRA-HIGH FREQUENCY ENERGY, ACCORDING TO A PROGRAMMED RADIATION PATTERN, COMPRISING: A WAVE GUIDE EXTENDING IN A PREDETERMINED PROPAGATION DIRECTION, HAVING AN ELONGATED APERTURE EXTENDING IN SAID DIRECTION; MASKING MEANS INCLUDING A WALL HAVING A RULED SURFACE HAVING GENERATRICES; MEANS FOR MOVING SAID MEANS, IN SUCH A WAY THAT ONE OF SAID GENERATRICES IS ALWAYS APPLIED TO SAID APERTURE, SAID WALL HAVING A PLURALITY OF ROWS OF SLOTS, EXTENDING ALONG SPACED GENERATRICES THEREOF, THUS UNMASKING SPACED RADIATING SLOTS IN SAID GUIDE. 